Edgards Voucher Rejected

I received an Edgers voucher on my account to the value of R7500 off any spend. I went to the Edgars in Centurion mall to redeem my voucher on 16 January 2018 as it expires 21 January 2018. When I got to the till they said the voucher code was invalid which was embarrassing as they had to call the manager, Jerry. I showed Jerry that this voucher is on my account and he said he would investigate. I called each day to get feedback where each time I was told they are still investigating. Jerry informed me that he will have the issue sorted out by Friday 19 January 2018 and he told me that Edgars can not issue a voucher to a customer and then change it to invalid, with the feedback I was patient. I received feedback this afternoon just stating that the matter is under investigation with no other details just like the rest of the week. This is not sorting out the issue as promised and I am a very unsatisfied customer.